Such internal combustion engines are described in the prior art.
For example, DE 2718162 A1 describes an air-cooled one-cylinder two-stroke internal combustion engine comprising one cylinder with at least exhaust and overflow ducts, a two-piece crankcase and a crankshaft held in its bearing in the crankcase. This crankcase is split in the longitudinal direction of the cylinders to above the top edge of the exhaust duct. The joint plane runs through the crankshaft bearing and through the cylinder axis. The cylinder and cylinder head are made as a one-piece die-casting; cooling fins are formed on the cylinder head above the cylinder.
Furthermore, U.S. Pat. No. 4,763,619 discloses a multi-cylinder internal combustion engine with a split engine block of cast construction in which the joint plane runs through the crankshaft bearing and the cylinder axes. The two engine halves are joined by studs passed through the entire crankcase. The cylinder sleeves are made together with a cylinder head as a one-piece die-casting and are joined interlockingly with the engine halves by a clamping device. Coolant flows through the intermediate space between engine block and cylinder sleeves.
In both cited prior-art internal combustion machines, the cylinder heads cast in one piece together with the cylinder sleeves form a complex casting, which can be made only with great expense by using cores. In addition, the cylinder heads must be particularly stable, since they extend well beyond the crankcase. A further disadvantage of the one-piece construction is that the entire component comprising cylinder sleeves and cylinder head must be replaced if repairs are needed, even if only one sleeve or one part of the cylinder head is damaged.
Finally, it is known (German Utility Model 1993272) that a watercooled one-cylinder two-stroke engine can be assembled from two crankcase halves split in the direction of the crankshaft axis, each being made as a one-piece casting. Thus the cylinder head is already formed at the same time, and so certain requirements must be imposed on the production of the cast shape. A suggestion on how to cast a multi-cylinder internal combustion engine cannot be inferred from the document.
U.S. Pat. No. 5,429,080 describes an internal combustion engine in which two crankcase halves, in each of which there is inserted a cylinder sleeve and a cylinder cover, are joined together. The said cylinder covers are provided with valve guides and inlet and exhaust ducts, and project beyond the top part of the crankcase. In that invention the joint plane of the crankcase halves runs parallel to the direction of the cylinder axis and perpendicular to the crankshaft axis, leading in the case of a multi-cylinder internal combustion engine to a plurality of partial half-shells, each assembled as one-cylinder modules, which in turn are assembled as an engine block, whereby the gaskets are correspondingly very complex. The cylinder covers projecting beyond the crankcase require a correspondingly massive construction for strength reasons.